"Thanks to everyone for you kind messages," he tweeted in French. "Very touched".
This is the French comedian's second child, as he is already father to a 12-year-old son named Noé from his relationship with French actress Anne Brochet, but Gad has expressed his excitement at Charlotte becoming a first-time mother.
He has described 27-year-old girlfriend as "generous and loving", and said that she would be "the best mother in the world".
Raphaël's birth was announced by the president of the National Council, Laurent Nouvion, at a late meeting of the High Assembly. "The royal family has a new member," he said.
Princess Charlene and Prince Albert of Monaco were the first visitors to congratulate Charlotte in Monaco's Princess Grace Hospital, in the same maternity ward where Charlotte herself was born. While Gad is not of royal birth, he is reported to be fitting in perfectly, and has previously said that Princess Caroline laughs at his jokes.
"I'm the happiest man," he said of his relationship with Charlotte. "Really, I am. I am lucky to be with her".